“The idea that breakfast is important for weight or that it kick-starts your metabolism is well ingrained,” says Enhad Chowdhury, a teaching fellow at the University of Bath in England. “And people who typically consume breakfast do weigh less than those who skip.” (Roughly 20 to 30 percent of adults skip breakfast.) But that’s not proof that skipping breakfast causes weight gain. Something else about breakfast eaters could make them leaner.